Bill acceptors can generally be sub-divided into two groups, namely a universal type bill acceptor and bill acceptors which are currency specific. Universal bill acceptors achieve this result through the provision of sensors which are able to read data from large areas or by the provision of many standard type sensors. In the first case, the quality of recognition is negatively affected and in the second case, the cost for the unit is quite high.
It can be appreciated the advantages possible with the universal acceptor in that the cost per unit can generally drop due to the larger number of units being manufactured. However, the sophistication of the unit has to increase quite dramatically.
It is now generally the practice to design a particular bill acceptor for a particular national currency. Each currency validator involves some preliminary research to determine what areas are to be scanned and what combination of different type of sensors are effective in providing the necessary quality. In addition, most currency validators are designed to be very reliable. However, when service is required, it tends to be quite specific and requires skilled technicians.